Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$45.73	13.338%	$51.8295	$51.83	$51.85	$51.80
Purchase #2	$38.39	11.290%	$42.7242	$42.72	$42.70	$42.70
Purchase #3	$44.96	6.381%	$47.8289	$47.83	$47.85	$47.80
Purchase #4	$101.60	5.540%	$107.2286	$107.23	$107.25	$107.20
Purchase #5	$90.84	6.237%	$96.5057	$96.51	$96.50	$96.50
Purchase #6	$153.83	7.187%	$164.8858	$164.89	$164.90	$164.90
Purchase #7	$92.36	3.611%	$95.6951	$95.70	$95.70	$95.70
7 purchase totals =	$567.71		$606.6978	$606.71	$606.75	$606.60